How to merge/join/append/concatenate files in VB6 with FileSystemObject

Private Sub Command1_Click()
    Dim folder    As String
    Dim dest_file As String
    Dim file_ext  As String
   
    Dim lPid      As Long
    Dim shellStr  As String
    Dim rvShellStr  As String
    rvShellStr = ""
   
   
    folder = "C:\myFolder\mySubFolder\"
    dest_file = "MergeFileName"
    file_ext = "*.txt"
   
    Dim srcFolder As String
    srcFolder = folder + file_ext
    Dim destFile As String
    destFile = folder + dest_file + ".txt"
   
    '------------------------------------------
    'kill target file
    '------------------------------------------
    On Error Resume Next
    Kill destFile
   
    '------------------------------------------
    'get file list from source file
    '------------------------------------------
    Dim fileArray() As String
    fileArray = Me.FileList(srcFolder)
   
    '------------------------------------------
    'ConcatenateFiles
    '------------------------------------------
    Call ConcatenateFiles(folder, destFile, fileArray)
   
    '------------------------------------------
    'all done
    '------------------------------------------
    MsgBox ("All Done")
End Sub

Public Function FileList(Mask As String) As String()

Dim sWkg As String
Dim sAns() As String
Dim lCtr As Long

ReDim sAns(0) As String
sWkg = Dir(Mask, vbNormal)

Do While Len(sWkg)

    If sAns(0) = "" Then
        sAns(0) = sWkg
    Else
        lCtr = UBound(sAns) + 1
        ReDim Preserve sAns(lCtr) As String
        sAns(lCtr) = sWkg
    End If
    sWkg = Dir
Loop

FileList = sAns
End Function
Private Sub ConcatenateFiles(ByVal folder As String, ByVal ResultFile As String, _
                                    SourceFiles() As String)
   
    ' Concatenate a variable number of text files into a single result file
'
' Params:
'  - ResultFile: the complete path of the result file you want to create
'  - Separator: a string that is written when a file is added to the result
' file.
'      Note: this string can contain the #FilePath# tag that will be replaced
'      with the path of the file being added
'  - SourceFiles: a sequence of files whose content will be concatenated
'
' Example:
'   ConcatenateFiles "D:\res.txt", "------ NEW FILE: #FilePath# ------",
'  "D:\1.txt", "D:\2.txt", "D:\3.txt"
Dim Separator As String
Separator = vbCrLf
Dim FSO As New Scripting.FileSystemObject
    Dim fsSourceStream As TextStream
    Dim fsResStream As TextStream
    Dim sSeparator As String
    Dim i As Integer
   
    On Error Resume Next
   
    ' create a new file
    Set fsResStream = FSO.OpenTextFile(ResultFile, ForWriting, True)
   
    ' for each source file in the input array
    For i = 0 To UBound(SourceFiles)
        ' add the separator first (replacing the special tag for the file path)
         Dim sourceFileName As String
        sourceFileName = folder + SourceFiles(i)
'        sSeparator = Replace(Separator, "#FilePath#", SourceFiles(i))
'        fsResStream.Write sSeparator & vbCrLf
'        ' open the file in read mode
        Set fsSourceStream = FSO.OpenTextFile(sourceFileName, ForReading)
        ' add its content + a blank line to the result file
        fsResStream.Write fsSourceStream.ReadAll ' & vbCrLf
        ' close this source file
        fsSourceStream.Close
    Next i
   
    fsResStream.Close
End Sub